Operator ride enhancement system

ABSTRACT

An operator ride enhancement system that is coupleable to the frame of a vehicle includes a counterweight platform moveably coupled to the frame, and a resilient member engaged with the frame and the counterweight platform. The mass of the counterweight platform is configured to be approximately at least equal to a total mass supported by the counterweight platform during operation of the vehicle. The operator ride enhancement system attenuates and/or inhibits movement of the counterweight platform during operation of the vehicle.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. provisional application No.61/327,434 filed Apr. 23, 2010, which is hereby incorporated byreference as if fully set forth herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND

The present disclosure relates generally to an operator ride enhancementsystem. More particularly, the disclosure describes an operator rideenhancement system incorporating a counterweight platform that ismoveably coupled to a vehicle frame and configured to isolate anoperator supported on the counterweight platform from disturbances ofthe vehicle.

Repeatedly subjecting a vehicle operator to disturbances (e.g.,undulations, etc.) that occur during operation of the vehicle can resultin the operator becoming uncomfortable. For example, the operator of alift truck often stands on an operator platform while controlling thelift truck. Various disturbances occur, for instance, as the lift trucktravels along a floor, over expansion joints, across dock plates, andmanipulates the forks. Increased focus on efficiency, through increasedproduction, has resulted in faster moving lift trucks, which exacerbatesthe occurrence and amplitude of the disturbances. Isolating the operatorfrom these and other disturbances may increase operator comfort,especially over prolonged periods of operation.

One technique that has been explored to suppress disturbances involvessuspending or supporting the typical, standard platform with a varietyof energy absorbing devices (e.g., springs, viscous dampers, rubberbumpers, etc.). However, many of these arrangements are dependent uponconfigurations that require adjusting or calibrating the energyabsorbing devices to accommodate operators of different mass (and hence,weight). Furthermore, these devices often result in increased complexityand maintenance. The remaining less sophisticated arrangements havelimited capability to attenuate the transmission of the disturbancesover a range of frequencies and amplitudes.

In light of at least the above considerations, a need exists forreducing disturbances experienced by a vehicle operator to enhance theoperator's ride on the vehicle.

SUMMARY

An operator ride enhancement system that is coupleable to the frame of avehicle includes a counterweight platform moveably coupled to the frame,and a resilient member engaged with the frame and the counterweightplatform. The mass of the counterweight platform is configured to beapproximately at least equal to a total mass supported by thecounterweight platform during operation of the vehicle. The operatorride enhancement system attenuates and/or inhibits movement of thecounterweight platform during operation of the vehicle.

In one aspect, an operator ride enhancement system for use in a vehiclehaving a frame, comprises a counterweight platform defining a mass, thecounterweight platform is coupled to the frame for pivotal movementabout an axis. A resilient member is engaged with the frame and thecounterweight platform to attenuate movement of the counterweightplatform about the axis. A control member is engaged with the frame andthe counterweight platform to inhibit movement of the counterweightplatform along the axis. The mass of the counterweight platform isconfigured to be approximately at least equal to a total mass supportedby the counterweight platform during operation of the vehicle.

In another aspect, an operator ride enhancement system for use in avehicle having a frame and defining an operator compartment, comprises acounterweight platform defining a mass, the counterweight platform ismoveably coupled to the frame at least partially within the operatorcompartment. A resilient member is engaged with the frame and thecounterweight platform. The mass of the counterweight platform isconfigured to be approximately at least equal to a total mass supportedby the counterweight platform during operation of the vehicle. The massof the counterweight platform and the resilient member are configured toattenuate disturbances transmitted through the frame to thecounterweight platform.

These and still other aspects of the invention will be apparent from thedescription that follows. In the detailed description, preferred exampleembodiments will be described with reference to the accompanyingdrawings. These embodiments do not represent the full scope of theinvention; rather, the invention may be employed in many otherembodiments. Reference should therefore be made to the claims fordetermining the full breadth of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear isometric view of an example vehicle incorporating anoperator ride enhancement system.

FIG. 2 is a partial isometric view of a portion of an example operatorride enhancement system.

FIG. 3 is a partial isometric view of the example operator rideenhancement system of FIG. 2.

FIG. 4 is a simplified isometric view of a portion of the exampleoperator ride enhancement system of FIG. 2.

FIG. 5 is an isometric exploded view of the operator ride enhancementsystem of FIG. 3.

FIG. 6 is a simplified side view of a portion of an alternative exampleoperator ride enhancement system showing an example operator backrestconfiguration.

FIG. 7 is a partial rear isometric view of another example operator rideenhancement system.

FIG. 8 is a partial rear isometric view of the operator ride enhancementsystem of FIG. 7.

FIG. 9 is a partial section view along line 11-11 of FIG. 8.

FIG. 10 is a partial isometric view of a further example operator rideenhancement system.

FIG. 11 is a partial isometric view of the operator ride enhancementsystem of FIG. 10.

FIG. 12 is a partial isometric view of yet a further example operatorride enhancement system.

FIG. 13 is a partial isometric view of another example operator rideenhancement system.

FIG. 14 is an isometric view of a further example operator rideenhancement system removed from a vehicle.

FIG. 15 is a partial top view of an additional example guide.

DETAILED DESCRIPTION OF THE PREFERRED EXAMPLE EMBODIMENTS

Several example embodiments of an operator ride enhancement system aredescribed and illustrated in the context of a material handling vehiclecommonly referred to as a lift truck. However, given the benefit of thisdisclosure, one skilled in the art will appreciate the variousmodifications that can be made to the example embodiments and thevarious applications in which the operator ride enhancement system maybe incorporated. For instance, the operator ride enhancement systemconcepts described herein may be applied to other material handlingvehicles as well as other devices where attenuating disturbancestransmitted to an operator or coupled structure/device is beneficial.Furthermore, the terms “fore,” “aft,” “front,” “back,” “side,” “top,”“bottom,” “up,” “down,” “raised,” “lowered,” “vertical,” “horizontal,”and other relative directional terms used herein are not to be limiting,but instead are used for convenience in describing the illustratedexample embodiments.

An example material handling vehicle, in the form of a lift truck 10(“lift truck”), is illustrated generally in FIG. 1. The lift truck 10includes a mast 12 operatively coupled to the fore end of the lift truck10 and capable of raising and lowering a set of forks 14 attached to themast 12. A pair of drive wheels (not shown) are rotationally coupled tothe fore end of the lift truck 10 and operationally engaged with a drivesystem (not shown), such as one or more electric motors. When the lifttruck 10 incorporates an electrical drive system, the lift truck 10includes a battery compartment that houses a battery 18, as isunderstood by one of ordinary skill in the art. In the exampleillustrated in FIG. 1, a steering wheel 20 operates in conjunction withthe drive wheels to allow the lift truck 10 to travel along a floor 22.

An operator compartment 24 is located near the aft end of the lift truck10 and includes a console 26 having operator controls 28 that allow anoperator to control the movement of the lift truck 10, the mast 12, andthe forks 14. The operator compartment 24 can also include an armrestand a backrest to accommodate an operator during use of the lift truck10.

When an operator enters the operator compartment 24, the operator stepsup and into the operator compartment 24. In one embodiment, a pedalswitch 34 is positioned within the operator compartment 24, such thatthe location of the pedal switch 34 and operator controls 28 typicallyresult in the operator assuming a left-facing stance. If an armrestand/or backrest are provided, preferably, the operator's back isproximate the backrest and the operator's right arm engages the armrestwhile the operator is in the left-facing stance.

With continued reference to FIG. 1 and additional reference to FIGS. 2-5an example embodiment of an operator ride enhancement system 36 is shownmoveably coupled to a frame 38 of the lift truck 10. The “frame” isdefined broadly to include any structure of the lift truck 10 suitableto support the mass of and the mass supported by the operator rideenhancement system 36 during use.

In one example embodiment, the operator ride enhancement system 36includes a counterweight platform 40, a resilient member 42, and acontrol member 44. The counterweight platform 40 is shown constructed ofa hinged portion 46 and a platform portion 48 that partially overlap andare coupled via fasteners 50, which may make assembly and installationeasier as the mass of the counterweight platform 40 may be cumbersome tomanipulate. In other forms, the counterweight platform 40 may be formed(e.g., cast, machined, molded, and the like) as a unitary body. Thecounterweight platform 40 of the example embodiment shown in FIG. 5 iscast from iron (such as grey iron, ductile iron 85-55-06, or mayalternatively be made of ASTM A36 grade steel alloy or any othersuitable material having sufficient density to provide the requisitecounterweight) and has a weight on the order of three hundred and fiftypounds. In one form, the counterweight platform 40 includes a base madeof low carbon steel that is approximately three inches thick with a thinangled top plate secured to the base (having a total weight ofapproximately three hundred and eighty-five pounds). In a preferredform, the counterweight platform 40 is tapered such that the interfacebetween the counterweight platform 40 and the operator is angled downrelative to horizontal at approximately 2° to 4°. Additionally, theunderside of the counterweight platform 40 may be angled up relative tohorizontal at approximately 2° to 4° to accommodate downward, pivotalmovement of the counterweight platform 40.

By providing a counterweight platform 40 having a mass in excess of themass required to perform the structural function of supporting a weightrange of operators (e.g., between approximately one hundred pounds andthree hundred and fifty pounds), the mass of the counterweight platform40 reduces the influence that the total mass supported by thecounterweight platform 40 during use (including the mass of theoperator) has on the overall dynamic response of the operator rideenhancement system 36. For instance, the variable mass of each operator(i.e., different operators may define different masses) has a diminishedimpact on the dynamic response of the operator ride enhancement system36 as the mass of the operator represents a reduced percentage of theoverall mass (i.e., the sum of the mass of the counterweight platform 40and the total mass supported by the counterweight platform 40).Therefore, the attenuation characteristics of the operator rideenhancement system 36 may be designed to maintain the typical dynamicresponse of the operator ride enhancement system 36 within a predefinedrange of characteristics (e.g., frequency range, maximum amplitude,maximum cycles post-disturbance, etc.) given that the mass of thecounterweight platform 40 dominates the dynamic response. The mass ofthe counterweight platform 40 may be equal to or greater than theexpected mass of the range of operators (e.g., approximately forty-fivekilograms to approximately one hundred and sixty kilograms), about equalto or greater than the mass of a particular operator, or preferablyapproximately at least equal to the total mass supported by thecounterweight platform 40.

Returning to the counterweight platform 40, the hinged portion 46includes a pair of axially aligned bores 51 at a hinged end 52. Eachbore 51 receives a post 54 that extends from a respective mounting block56. A spacer 58 is slid over each post 54 and positioned against abearing face 60 of the mounting block 56. A spherical bearing 62 is thenfit over each post 54 and fit within the respective bore 51. Themounting blocks 56 are secured to the frame 38 via fasteners 64 suchthat the hinged portion 46 and coupled platform portion 48 can pivotabout an axis A (shown generally in FIG. 3) that is substantiallyparallel with a fore-aft axis of the lift truck 10. In preferred forms,the pivot arm (i.e., the approximately perpendicular distance from theaxis A to the distal end of the counterweight platform 40) is as long aspossible to more closely approximate linear, vertical movement of theoperator supported on the counterweight platform 40 as it pivots througha relatively acute arc (e.g., 3°-5° and typically less than 3°).

It is preferred, in some configurations, to have the substantiallyhorizontal axis A about which the counterweight platform 40 pivots beoriented substantially parallel with the fore/aft orientation of thelift truck 10 to minimize the inertial disturbances that may occur aboutan axis that is oriented more perpendicular to the fore/aft orientationof the lift truck 10. If the axis A is perpendicular to the fore/aftorientation of the lift truck 10, the counterweight platform 40 may havea tendency to rotate about the perpendicular axis during accelerationand deceleration of the lift truck 10, thus a more parallel orientationof the axis A reduces the tendency of the counterweight platform 40during acceleration and deceleration to rotate about the axis A. Otherorientations of the axis A are available depending upon the particularapplication requirements for the operator ride enhancement system 36.

With continued reference to FIGS. 1-5, the example embodiment of theoperator ride enhancement system 36 includes the resilient member 42.The example resilient member 42 may be one or more helical springscaptured in a cylindrical housing between a fixed end plate and aplunger slideably positioned within the cylindrical housing. The plungermay also function as a dampener member by frictionally engaging thecylindrical housing as it slides. Alternatively, the plunger may dividethe cylindrical housing into two chambers such that a fluid is urgedthrough an orifice between chambers as the plunger slides within thecylindrical housing. One example embodiment of the resilient member 42may include that described in U.S. Pat. No. 6,773,002, which is herebyincorporated by reference as if fully set forth herein. The resilientmember 42 may further include an auxiliary spring at the extreme end ofthe stroke of the plunger, thereby providing additional resilience forsevere disturbances. In addition, as shown in FIG. 5, a bumper 43 may besecured (e.g., via a fastener 47) to the underside of the counterweightplatform 40. The example bumper 43 is elastomeric and configured toestablish a flexible interface between the frame 38 and the underside ofthe counterweight platform 40 in the event that the counterweightplatform 40 over pivots about the axis A.

The resilient member 42 is engaged with the frame 38 and thecounterweight platform 40 to at least partially attenuate disturbancesimparted through the frame 38 to the counterweight platform 40 when thelift truck 10 is in use (e.g., as the lift truck 10 travels along thefloor 22, over an expansion joint, along a loading dock ramp, into astorage container, and the like). Specifically, the example resilientmember 42 includes a first end 74 attached to the frame 38 via a clevis76 extending from the frame 38, and a second end 78 attached to thecounterweight platform 40 via a clevis 80 extending, in the exampleembodiment, from the hinged portion 46 of the counterweight platform 40.

The resiliency (e.g., spring constant, elasticity, and the like) of theresilient member 42 is preferably selected in combination with the massof the counterweight platform 40 to control the maximum staticdeflection of the counterweight platform 40 as it pivots about the axisA, and to reduce the transmission of disturbances to the operatorsupported on the counterweight platform 40. Other considerations, suchas the natural frequency of the operator ride enhancement system 36 andthe maximum dynamic deflection of the counterweight platform 40, mayalso be factors in selecting/configuring a resilient member 42 for aspecific application. In one example form, a resilient member includes acoil spring having preload of approximately 1025 Newtons (approximately230 pounds force) and a spring rate of approximately 3300 Newtons percentimeter (approximately 1888 pounds force per inch).

In the example shown in FIGS. 1-5, the control member 44 inhibitsmovement of the counterweight platform 40 in the fore/aft directiongenerally along the axis A. The control member 44 may reduce undesiredmovement of the counterweight platform 40 in the fore/aft orientationduring acceleration and deceleration of the lift truck 10. Specifically,the control member 44 includes a first end 82 engaged with the frame 38and a second end 84 engaged with the counterweight platform 40 toinhibit movement of the counterweight platform 40 along the axis A(i.e., along the length of the control member 44). In the example shownbest in FIGS. 4 and 5, the control member 44 is in the form of a rodthat may be adjustable in length and include a knuckle 86 at the firstend 82 and another knuckle 86 at the second end 84, with fasteners 88securing the knuckles 86. Other forms of the control member 44 may used,such as a beam, a channel, a rigid damper, stiff spring, guideroller(s), and the like without departing from the scope of theinvention.

In some applications, the operator ride enhancement system 36 utilizesthe inherent damping within the system (e.g., frictional losses due tocompressing the spring in the resilient member 42, frictional lossesrelated to the spherical bearings 62, and the like), and therefore nodistinct dampener member is required. In other instances, for example,the resilient member 42 may further include a dampener member (e.g., ahydraulic shock absorber), separately or in combination with theresilient member 42, to provide the desired dampening of thecounterweight platform 40 and operator supported thereon. Dampenermembers integrated into the operator ride enhancement system 36 arepreferably configured to return the counterweight platform 40 to aneutral (i.e., static) position in a relatively short timepost-disturbance (e.g., within two cycles of the counterweight platform40) while still providing the application-specificdisturbance-attenuation capability.

As best shown in FIG. 2, during use, the platform portion 48 of thecounterweight platform 40 is positioned generally within the bounds ofthe operator compartment 24. A hinge shield 90 provides a generalseparation between the platform portion 48 and the hinged portion 46. Inthe preferred form, and in accordance with maximizing the mass withinthe available space, the counterweight platform 40 includes an arcuatesurface 92 that provides clearance for the steering wheel 20 (not shownin FIGS. 2-5 for clarity). In addition, the platform portion 48 caninclude a recess 35 sized to support and accommodate the pedal switch 34(shown in FIG. 1); the recess 35 may also include a drain opening 37 toreduce fluid retention near the counterweight platform 40 and around thepedal switch 34. The operator ride enhancement system 36 shown in FIG. 1may further include a covering in the form of a resilient mat 41 uponwhich an operator stands when within the operator compartment 24.

As a result of the operator ride enhancement system 36, disturbancesinput to the frame 38 of the lift truck 10 are at least partiallyattenuated due to the configuration and arrangement of the variouscomponents of the operator ride enhancement system 36. Furthermore, asnoted above, the mass of the counterweight platform 40 minimizes thedynamic influence resulting from operators of varying mass.

Turning to FIG. 6, a simplified alternative arrangement of thecounterweight platform 40 and a backrest 32 are shown. In theillustrated configuration, a distal end 96 of the counterweight platform40 is pivotally coupled to a lower end 98 of a link 100 that extendsbetween the counterweight platform 40 and the backrest 32. Specifically,an upper end 102 of the link 100 is pivotally coupled to the backrest32. The backrest 32 is slidable up and down (shown by arrows 104), suchas by rollers 106 extending from the backrest 32 and engaged with atrack 108 fixed to the frame 38. As the counterweight platform 40deflects and/or pivots about the axis A (shown simplistically by dashedline 110), the distal end 96 of the counterweight platform 40 andcoupled lower end 98 of the link 100 are moved down to point B. Thisresults in the backrest 32 translating downward accordingly such thatrelative movement between the operator, counterweight platform 40, andbackrest 32 is minimized.

Another example embodiment of an operator ride enhancement system 36 isgenerally illustrated in FIGS. 7-9. The operator ride enhancement system36 incorporates a counterweight platform 112 formed (e.g., machined) ofa single body and having a pair of arms 114, 116 hinged to a centralizedmounting block 118. The mounting block 118 is fixed to the frame 38 viafasteners 120 (best shown in FIGS. 8 and 9). Additionally, the operatorride enhancement system 36 includes a pair of resilient members 42having a first end engaged to the counterweight platform 112 and asecond end mounted to the frame 38. One of the resilient members may bemounted as described in reference to FIGS. 1-5, alternatively, or inaddition, the resilient member 42 may be mounted to a side portion 122of the frame 38. Thus, as illustrated, the resilient member(s) 42,similar to the other components (e.g., dampener member(s), controlmember(s), etc.), may be mounted in a variety of locations relative tothe counterweight platform 40 (and axis A), but is preferably mounted tonot interfere with the operator. Furthermore, the resilient member 42 isdesigned to account for the static and dynamic forces acting on theresilient member 42 given the particular mounting location.

A control member 124 (shown in FIG. 8) is preferably adjustable inlength and includes a first end 126 pivotally coupled to the frame 38and a second end 128 pivotally coupled to the counterweight platform112. A rubber bushing is preferably seated in the first end 126 andsecond end 128 of the control member 124. A fastener 130 secures thefirst end 126 to a clevis 132 that is in turn fastened to the frame 38.Also, another fastener 130 secures the second end 128 to another clevis134 that is in turn fastened to the counterweight platform 112. Again,the control member 124 inhibits movement of the counterweight platform112 generally in a direction along a pivot axis A about which thecounterweight platform 112 may rotate.

With specific reference to FIGS. 7 and 9, the counterweight platform 112is shown pivotally coupled to the frame 38 via mounting block 118. Themounting block 118 defines a pair of aligned bores 136. Each bore 136receives a shaft 138 extending through an opening 140 in respective arms114, 116 of the counterweight platform 112. The outer end of the shaft138 includes a tab 142 radially extending from the shaft 138 thatprevents the shaft 138 from sliding through the opening 140 in therespective arm 114, 116. As best shown in FIG. 7 a fastener 144 extendsthrough an opening in the tab 142 and is fastened to the respective arm114, 116, thereby securing the shaft 138 to the respective arm 114, 116and in the respective bore 136.

The opposite end of the shafts 138 accept a radial spherical bearing 146that is inserted into the respective bore 136 in the mounting block 118.Therefore, the counterweight platform 112 is hinged to the mountingblock 118, and hence frame 38, such that the counterweight platform 112may pivot about the axis A. As with the previous example operator rideenhancement system 36, a dampener member (e.g., a hydraulic shockabsorber) may be engaged between the frame 38 and the counterweightplatform 112 to attenuate disturbances input to the frame 38, therebyultimately reducing the transmission of the disturbance to thecounterweight platform 112 and operator supported thereon.

Another example embodiment of an operator ride enhancement system 36 isillustrated generally in FIGS. 10 and 11. In this arrangement, acounterweight platform 148 includes a single arm 150 that is hinged tothe frame 38 at a distal end 152. Specifically, the arm 150 includes asquare opening 154 through which a resilient member in the form of asquare torsion bar 156 is rotatably interlocked, such that pivoting thecounterweight platform 148 about the axis A applies a rotational torqueto the torsion bar 156. Given that one end 158 of the torsion bar 156 isrotatably fixed to the frame 38 via a preload member 160 and theopposite end 162 of the torsion bar 156 is rotatably captured to theframe 38 via a bracket 164, the counterweight platform 148 is pivotallycoupled to the frame 38.

The preload member 160 is fixed to the torsion bar 156 and rotatablycoupled to the frame 38 such that rotating the preload member 160 altersthe static location of the counterweight platform 148. For instance, thepreload member 160 includes an adjustment bolt 166 that extends into andthrough a threaded opening in the preload member 160. A tip 168 of theadjustment bolt 166 bears against the frame 38 urging the torsion bar156 to rotate about the axis A in a direction to move the counterweightplatform 148 upward, and thus reducing the static deflection fromhorizontal.

A dampener member in the form of an elastomeric bushing 170 frictionallyengages the end 162 of the torsion bar 156 and is supported by thebracket 164. As a result, the elastomeric bushing 170 at least partiallyattenuates the disturbances imparted through the frame 38 to thecounterweight platform 148 and helps reduce the oscillations of thecounterweight platform 148 that may occur in response to thedisturbances. Of course, the dampener member may include a variety ofconfigurations, such as a hydraulic damper, a pneumatic damper, amagneto-rheological damper, an electro-rheological damper, and afriction damper. One skilled in the art, given the benefit of thisdisclosure will appreciate the variety of dampener member devices andarrangements.

In another example operator ride enhancement system 36 illustrated inFIG. 12, a counterweight platform 172 may be hinged to the frame 38similar to that shown and described with reference to FIGS. 10 and 11,but may also include resilient members in the form of compressionsprings 175. The springs 175 are illustrated as being positioned betweenthe counterweight platform 172 and a subfloor 174 that is secured to theframe 38. Additionally, a dampener member 176 (shown in simplified form)may be engaged between the counterweight platform 172 and the frame 38to again inhibit movement of the counterweight platform 172 during use.

Turning next to FIG. 13, another alternative example operator rideenhancement system 36 is illustrated. This embodiment includes acounterweight platform 178 having a pair of arms 180, 182 extendingupward and away from the counterweight platform 178 toward a pair ofmounting blocks 184 that are secured to the frame 38. A resilientmember, in the form of one or more springs 186 is again positionedbetween the counterweight platform 178 and a subfloor 188. Given thebenefit of this disclosure, one skilled in the art will appreciate thatthe resilient member may alternatively be any other suitable device,such as an extension spring, a torsion spring, an air spring, and anelastomeric spring.

Additionally, or alternatively, a torsion bar 190 may be fixed to theframe 38 and one or more of the arms 180, 182 such that rotating thecounterweight platform 178 about the axis A established by the mountingblocks 184 torques the torsion bar 190.

A further example operator ride enhancement system 36 is illustrated inFIG. 14. In this embodiment, the operator ride enhancement system 36includes a counterweight platform 192 that is not hinged to the frame38, but is instead supported by a sub-frame 194 that is fixed to theframe 38 (not shown). The counterweight platform 192 includes a seriesof guides in the form of vertical cylindrical passageways 196 into whichguide pins 198 (extending upward from the sub-frame 194) engage. Thecylindrical passageways 196 may be lined with bearings to aid relativemovement of the counterweight platform 192. As a result, thecounterweight platform 192 can translate vertically along the axis ofthe guide pins 198 during use in response to disturbances, as the guidepins 198 are slideably received in the vertical cylindrical passageways196.

Resilient members in the form of coil springs 200 are located betweenthe sub-frame 194 and the counterweight platform 192 to at leastpartially attenuate disturbances imparted through the frame 38 to thecounterweight platform 192. A dampener member in the form of a hydraulicshock absorber (not shown) may also be secured to the counterweightplatform 192 with an upper end of the dampener member fixed to the frame38 (not shown). As a result, the hydraulic shock absorber at leastpartially attenuates the disturbances imparted through the frame 38 tothe counterweight platform 192.

An alternative guide is illustrated in FIG. 15. The guide 206 generallycomprises a channel 208 fixed to (or integral with) the frame 38 and acarriage 210 fixed to a counterweight platform 212. The carriage 210includes a roller 214 rotatably captured on a spindle 216. As such, thecarriage 210 (and thus counterweight platform 212) is captured withinand slides along the channel 208 as the roller 214 rolls.

The above-described operator ride enhancement systems may requireapplication specific adjustments to achieve desired levels ofdisturbance attenuation. Several general considerations may aid thedesign and development of a suitable operator ride enhancement systemgiven particular application requirements. For instance, whenconsidering a resilient member, higher spring rates are generally lesssensitive to variances in operator mass and result in less staticdeflection of a counterweight platform supporting a mass. In someapplications, a balance must be struck between the natural frequency,static deflection, dynamic deflection, spring rate, and counterweightplatform mass. The counterweight platform mass is often restricted bypackaging limitations; however, other options for increasing the mass ofthe counterweight platform may include rearranging various vehiclecomponents, such as motors, controllers, hydraulics, etc. to alter thedynamics of the operator ride enhancement system. As a specific example,a battery of a fork truck may be structurally coupled to a counterweightplatform, thereby substantially increasing the mass of the counterweightplatform as compared to the mass of an operator, further reducing theimpact that the mass of an operator has on the dynamic response of theoperator ride enhancement system.

While there has been shown and described what is at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications can be made,given the benefit of this disclosure, without departing from the scopeof the invention defined by the following claims.

I claim:
 1. An operator ride enhancement system for use in a vehiclehaving a frame, the operator ride enhancement system comprising: acounterweight platform defining a mass and coupled to the frame forpivotal movement about an axis; a resilient member engaged with theframe and the counterweight platform to attenuate movement of thecounterweight platform about the axis; and a control member engaged withthe frame and the counterweight platform to inhibit movement of thecounterweight platform along the axis; wherein the axis is orientedsubstantially parallel with a fore-aft axis of the vehicle; wherein thecontrol member is oriented substantially parallel with the fore-aft axisof the vehicle; and wherein the mass of the counterweight platform isconfigured to be approximately at least equal to a total mass supportedby the counterweight platform during operation of the vehicle.
 2. Theoperator ride enhancement system of claim 1, wherein the counterweightplatform comprises: a hinged portion pivotally coupled to the frame; anda platform portion coupled to the hinged portion; wherein the platformportion is tapered toward a distal end that is opposite to the hingedportion.
 3. The operator ride enhancement system of claim 1, wherein themass of the counterweight platform is configured to be at leastforty-five kilograms.
 4. The operator ride enhancement system of claim1, wherein: the resilient member is a spring; and the control member isa rod.
 5. An operator ride enhancement system for use in a vehiclehaving a frame, the operator ride enhancement system comprising: acounterweight platform defining a mass and coupled to the frame forpivotal movement about an axis; a resilient member engaged with theframe and the counterweight platform to attenuate movement of thecounterweight platform about the axis; and a control member engaged withthe frame and the counterweight platform to inhibit movement of thecounterweight platform along the axis; wherein the mass of thecounterweight platform is configured to be approximately at least equalto a total mass supported by the counterweight platform during operationof the vehicle; and wherein the counterweight platform is configured toat least partially surround a steering wheel of the vehicle.
 6. Theoperator ride enhancement system of claim 5, wherein: the axis isoriented substantially parallel with a fore-aft axis of the vehicle; andthe control member is oriented substantially parallel with the fore-aftaxis of the vehicle.
 7. An operator ride enhancement system for use in avehicle having a frame and defining an operator compartment, theoperator ride enhancement system comprising: a counterweight platformdefining a mass and moveably coupled to the frame at least partiallywithin the operator compartment; and a resilient member engaged with theframe and the counterweight platform; wherein the mass of thecounterweight platform is configured to be approximately at least equalto a total mass supported by the counterweight platform during operationof the vehicle; wherein the mass of the counterweight platform and theresilient member are configured to attenuate disturbances transmittedthrough the frame to the counterweight platform; and wherein theresilient member is a torsion member having a first end rotatably fixedto one of the frame and the counterweight platform and a second endrotatably fixed to the other of the frame and the counterweightplatform.
 8. The operator ride enhancement system of claim 7, whereinthe counterweight platform is pivotally coupled to the frame for pivotalmovement about an axis.
 9. The operator ride enhancement system of claim8, further comprising a control member engaged with the frame and thecounterweight platform to inhibit movement of the counterweight platformalong the axis.
 10. The operator ride enhancement system of claim 9,wherein the control member is at least one of a rod, a spring, a damper,and a roller.
 11. The operator ride enhancement system of claim 7,further comprising: a preload member proximate the first end of thetorsion member; and a dampener member engaged with the frame and thesecond end of the torsion member to at least partially attenuate thedisturbances transmitted through the frame to the counterweightplatform.
 12. The operator ride enhancement system of claim 7, whereinthe counterweight platform includes at least one arm extending from thecounterweight platform having a distal end pivotally coupled to theframe for pivotal movement about an axis.
 13. The operator rideenhancement system of claim 7, wherein the resilient member is at leastone of a compression spring, an extension spring, a torsion spring, anair spring, and an elastomeric spring.
 14. The operator ride enhancementsystem of claim 7, further comprising: a dampener member engaged withthe frame and the counterweight platform to attenuate the disturbancestransmitted through the frame to the counterweight platform; wherein thedampener member is at least one of a hydraulic damper, a pneumaticdamper, a magneto-rheological damper, an electro-rheological damper, anda friction damper.
 15. The operator ride enhancement system of claim 7,wherein the mass of the counterweight platform is configured to beapproximately at least forty-five kilograms.
 16. The operator rideenhancement system of claim 7, wherein the mass of the counterweightplatform is configured to be approximately at least one hundred andsixty kilograms.
 17. The operator ride enhancement system of claim 7,wherein the counterweight platform comprises: a hinged portion coupledto the frame for pivotal movement about an axis; and a platform portioncoupled to the hinged portion.
 18. An operator ride enhancement systemfor use in a vehicle having a frame and defining an operatorcompartment, the operator ride enhancement system comprising: acounterweight platform defining a mass and moveably coupled to the frameat least partially within the operator compartment; a resilient memberengaged with the frame and the counterweight platform; and at least oneguide coupled to the frame and engaged with the counterweight platformto allow the counterweight platform to translate along the guide inresponse to the disturbances; wherein the mass of the counterweightplatform is configured to be approximately at least equal to a totalmass supported by the counterweight platform during operation of thevehicle; and wherein the mass of the counterweight platform and theresilient member are configured to attenuate disturbances transmittedthrough the frame to the counterweight platform.
 19. The operator rideenhancement system of claim 18, wherein the resilient member is atorsion member having a first end rotatably fixed to one of the frameand the counterweight platform and a second end rotatably fixed to theother of the frame and the counterweight platform.
 20. An operator rideenhancement system for use in a vehicle having a frame and defining anoperator compartment, the operator ride enhancement system comprising: acounterweight platform defining a mass and moveably coupled to the frameat least partially within the operator compartment; a resilient memberengaged with the frame and the counterweight platform; and a backrestcoupled to the counterweight platform such that the backrest and thecounterweight platform move substantially in unison as the counterweightplatform moves relative to the frame; wherein the mass of thecounterweight platform is configured to be approximately at least equalto a total mass supported by the counterweight platform during operationof the vehicle; and wherein the mass of the counterweight platform andthe resilient member are configured to attenuate disturbancestransmitted through the frame to the counterweight platform.